Neuroscience has made remarkable progress in identifying the neural processes associated with conscious experience. Researchers can record patterns of neural activity, investigate their causal organisation, and examine how they change as perception changes. Yet an important question remains: does explaining the material organisation of the brain explain conscious experience itself?
The question is not whether consciousness depends on the brain. It is whether a complete description of the brain's material processes would, by itself, explain experience in its character as meaning.
The distinction may be easier to see from the perspective of language.
Two orders of experience
In systemic functional linguistics, we can distinguish two fundamental orders of experience: the first-order experience of the material world and the second-order experience of that world as construed through consciousness and meaning.
The distinction is not between two independent worlds. It concerns different orders of organisation.
Consider the sound of a familiar voice. We can describe the physical production of the sound, its acoustic properties, the physiological processes through which it is heard, and the neural activity associated with recognising it.
But hearing that voice as the voice of someone we love is not simply another description of the acoustic signal. The voice has a significance within the organisation of experience. Its meaning depends on relations that cannot be identified merely by describing its physical properties.
The material processes are indispensable. Without them, the voice would not be heard in this particular material occurrence. But describing those processes is not yet the same as explaining what the voice means.
The distinction is not peculiar to language. A sound can be a physical event, a signal, a warning, a promise or a memory. These are not interchangeable descriptions of the same thing. They locate what occurs within different organisations of relations.
If we confuse these orders, we risk assuming that a sufficiently complete description of the material event must also be a sufficient explanation of its significance.
When correlation became explanation
This brings us back to the problem of consciousness.
Identifying the neural correlates of an experience establishes relationships between neural activity and what an organism experiences or reports experiencing. Such research is essential. Without it, we would have little basis for understanding the biological conditions associated with conscious awareness.
But identifying a correlate is not necessarily the same as explaining the experience with which it correlates.
Consider the recent study of binocular rivalry in macaque monkeys. Researchers detected strong neural patterns associated with both a face image apparently perceived and another apparently suppressed from awareness. The finding challenges any simple assumption that the strength of a neural representation determines whether its content becomes conscious.
The experiment reveals something important about neural activity. It does not, by itself, explain the difference between the two images as experienced—or establish precisely how the monkeys experienced them.
The question is not resolved simply by collecting more neural data. More detailed measurements may reveal distinctions that earlier methods missed, and more sophisticated models may explain how those neural processes interact. But we must still ask what kind of explanation would account for the relationship between those processes and experience.
This problem remains even when a theory goes beyond correlation.
Giulio Tononi's Integrated Information Theory, for example, proposes that consciousness is identical to a system's intrinsic cause-and-effect organisation. It attempts to explain consciousness rather than merely identify its neural correlates.
That is a substantial theoretical advance in ambition. Yet the identification of a particular material organisation with consciousness remains a claim requiring justification. A precise description of causal relations does not, simply by virtue of its precision, establish that those relations explain experience in its subjective or semiotic character.
The issue is not that material explanations are inadequate because they are material. It is that the adequacy of an explanation depends on what it claims to explain.
The meaning of material organisation
We should not conclude that consciousness is independent of material processes, or that neuroscience cannot contribute to explaining it. The distinction between material and semiotic orders does not require us to treat them as separate substances.
Language itself provides a useful comparison. An utterance has a material occurrence, but its meaning cannot be identified simply with the acoustic or graphic properties of that occurrence. Its meaning depends on its place within a semiotic system and on the relations through which it functions.
The analogy does not prove that consciousness and language have identical structures. It does, however, expose a general problem in explanation: describing the material conditions under which something occurs is not automatically equivalent to explaining its organisation at another order.
The question is therefore not whether meaning has material conditions. It plainly does. The question is whether those conditions, described exclusively in material terms, are sufficient to explain the organisation of experience as meaning.
Perhaps we need to distinguish the material processes through which an experience is actualised from the semiotic organisation through which experience has significance.
That distinction would change how we approach the brain. Rather than assuming that consciousness must eventually be explained by extending a material description until nothing remains unmeasured, we could investigate how material processes participate in the organisation of experience.
The word participate matters here. It neither diminishes the causal importance of neural activity nor assumes that the relationship between neural processes and consciousness has already been understood. It leaves the relationship itself as something to be investigated.
The living relation
The brain is part of a living organism. Its organisation has a biological history, and its activity belongs to the continuing life of that organism. Edelman's account of neural selection draws attention to this history; Tononi's theory directs attention towards the intrinsic causal relations through which a system is organised.
Their approaches differ, but both invite us to look beyond isolated neural events.
A further question arises when we consider the organism's relations with its surroundings. What an event means for a living subject cannot necessarily be understood by considering the event's physical properties alone. Its significance depends on the organisation of the life in which it occurs.
This does not establish that the environment is itself part of the conscious system, or that consciousness extends beyond the brain. Those remain questions for investigation. It does suggest that we should be cautious about treating the brain as though its material description must, by itself, settle every question about the experience of the organism.
We may need to understand not only how neural processes are organised, but how that organisation belongs to the activity of a living subject whose experience has significance.
The distinction between material and semiotic orders is therefore not an obstacle to scientific explanation. It is a way of clarifying what an explanation needs to address.
Perhaps the difficulty is not simply that we have yet to discover how the brain produces consciousness. Perhaps we must also ask whether a description of material organisation, however complete, is sufficient to explain experience in its character as meaning.
The question is no longer only how the brain works, but how the material and semiotic orders of experience are related.
And that is a question about the organisation of relations, not merely the identification of things.
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